A technology solution that has been applied for thwarting car thefts involves a transmitter coupled to a location-determining device, such as one utilizing the Global Positioning System (GPS). Upon theft of a vehicle, the transmitter automatically broadcasts the stolen vehicle location without knowledge of anyone in the vehicle. Vehicles are often recovered intact and the thieves are often caught as well.
See, for example, U.S. Pat. No. 5,918,180 to Dimino (incorporated herein by reference). Dimino discloses a tracking system for monitoring and locating vehicles that includes a cellular telephone that is located in the vehicle, a global positioning system receiver also located within the vehicle, and an interface unit between the global positioning receiver and the telephone. The global positioning receiver communicates with a system of satellites and provides continuous data reflecting the present spatial location of the vehicle in terms of its latitude and longitude coordinates. The interface between the GPS receiver, and the wireless telephone includes a speech synthesizer circuit that converts the digitally encoded spatial coordinates into speech, so that position is enunciated through the cellular phone. Note, however, that the owner of the vehicle must call the vehicle cellular telephone to obtain the position information.
More recently, a similar technique has been proposed for preventing child abductions. The main challenge has been development of a small, lightweight and inexpensive portable package that consumes little power. Only in recent years have small, moderately priced GPS devices become commercially available. One proposed system, sold. under the trademark SatCell, includes a GPS receiver and a cellular telephone combined together in a single lightweight portable package. This package can report its location, heading and speed every 15 seconds, but only during an established cellular telephone connection. This allows a parent/guardian or other tracking entity (e.g., a security service) to monitor the position of a child bearing the portable package from a remote computer screen or other tracking unit. The location information is transmitted periodically during the cellular telephone call because it would be difficult to otherwise detect an abduction event and trigger the package to transmit only when there is an emergency.
Although such a system is readily implementable, there are many shortcomings, including availability, scalability, geographic coverage, and power consumption. Even with new battery technology, cellular phones consume power much more rapidly when in a transmit/receive mode as opposed to while in the stand-by mode. Further, a cellular call must be initiated before communication can take place. A captor or hijacker may move a person for an amount of time longer than during which the cell phone battery could last while in the transmit/receive mode. Note that it is known to determine a PCS subscriber's location using GPS. See, for example, U.S. Pat. No. 5,835,907 to Newman, assigned to the assignee of the present invention, and incorporated herein by reference. U.S. Pat. No. 5,835,907 discloses a wireless communication device, operating over frequencies allocated to Personal Communications Services (PCS), which uses GPS technology to determine the subscriber's exact location on a periodic basis. The device sends the location information to a database for storage and subsequent retrieval by a Geographical Information System (GIS) software application. The GIS converts the location information represented by a latitude/longitude combination to a user-friendly classification of a block, street, city, etc. The user-friendly classification of the subscriber's location is then automatically communicated to emergency services and/or a designated contact, if an emergency button has been activated on the device. Alternatively, the device responds to on-demand inquiries on the subscriber's location via a computer link or a computerized voice processing equipment, such as a Voice Response Unit (VRU). Such a system automatically transmits over a unidirectional link, location information and a unique code which identifies the PCS device to a computer network over a wireless medium, and selectively generates a distress signal responsive to activation by the user of the PCS device. This system is designed for overt use in an emergency, not for covert use in an abduction or runaway situation.